Mobile devices are often designed with tight power consumption constraints since a common design goal is to maximize battery life while minimizing battery size. While this design goal also applies to many other scenarios, a familiar scenario for this design goal is the mobile device. In addition to using low-power processors, mobile devices save on power consumption by going into sleep, hibernate, power-off, etc. modes by user instruction or automatically after the passage of time with no user activity.
Since mobile devices are often misplaced, stolen or misused, it is common for a mobile device to have a lock/unlock feature whereby a user can actively instruct the mobile device to lock and/or the mobile device might be programmed to lock automatically after the passage of time with no user activity. In some cases, the locking is followed by a powering-down of parts of the mobile device. Of course, it is often the case that an unlocking mechanism is not powered down, so that even a power-saving mobile device can be unlocked quickly by its user.
As one example, a mobile device might be designed with multiple functional subsystems where each subsystem has some functionality that is able to be powered up and powered down independently of other subsystems. Such a mobile device might have a touch processing subsystem that remains powered up while a processor subsystem and a radio frequency (“RF”) subsystem are powered down. That way, the touch processing subsystem is available to detect when the user attempts to unlock the mobile device via a touchscreen interface and, if successful, trigger the powering up of other subsystems, such as the processor subsystem, the RF subsystem, a modem subsystem, a display subsystem, etc.